The present invention relates to a roller for a rotary printing press drying assembly.
As is known, e.g. in printing paper material bands, a plurality of printing units including known ink applying devices are generally used.
Said printing units comprise drying assemblies, including a plurality of parallel rollers which, immediately after the printing cylinder of the printing unit, extend upward, and then downward, to convey the paper band toward a following printing unit.
The above mentioned drying assemblies operate to remove from the paper band the solvents of the just applied ink, while simultaneously drying said ink.
Since the bands to be printed, generally made of a paper material, are greatly hygroscopic, they, upon contacting the printing cylinder, absorb a comparatively great amount of ink and solvent particles, thereby causing the paper band to greatly expand.
Moreover, since the paper band is mainly stressed, as it is conveyed, by a pulling force, the longitudinal expansions are integrally compensated for, whereas the cross expansions of the paper band cannot be compensated for and, accordingly, as the paper band passes through the series of parallel rollers of the ventilating assembly, a plurality of comparatively narrow creases extending in the band feeding direction are formed.
In a finished product, said creases would constitute a waste generating defect, with a consequent yield decrease.